What do you mean by jackrabbit? I didnt think you could fit anything bigger than 14 AH. the 18AH's are too tall but I dont put the cover on. Maybe that also keeps the batts. from getting hot. and the fifth is under seat. Example: 5 x 18ah = 90ah AND 20ah x 4 = 80ah ?

Hee hee. "Jackrabbit" means full throttle off the line, using those extra volts to zoom away. The catch is that it uses far more current to enjoy the power than slowly rationing it out with gentle starts and moderate speeds.

The batteries in my XB600 were four 20 AH units:

They fit in like this (after I rewired the pack to 10GA/soldered terminals rather than the stock 14GA/ crimped terminals):

Battery overheating can be a REAL problem. If yours are getting above warm, you are either putting too much current in on charge or drawing too much out in discharge.

An example of what NOT to do:

A dried out battery in the pack never came up to full voltage, and the charger just kept running. The pack HAD lasted two years.